It’s a common practice and one of the few “moral rights” recognized in the Berne Convention:

Article 6bis
Moral Rights:
1. To claim authorship; to object to certain modifications and other derogatory actions;
2. After the author’s death; 3. Means of redress

(1) Independently of the author’s economic rights, and even after the transfer of the said rights, the author shall have the right to claim authorship of the work […]

Edit to add: Death to Copyright Laws!